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Hesitation after slowing or stopping at junctions
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Posted 4/14/2019 1:43 PM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
Hesitation after slowing or stopping at junctions

Hi All

Hoping someone can help me with this problem..

When slowing or almost stopping at a junction (or turn) the engine dies / stumbles / hesitates to the extent that I am making sure I have no traffic approaching (if pulling out of a junction)

So far I have :

1) checked the HT plug leads & cleaned the coil pack electrical connectors
2) ran through two full premium grade tanks of fuel
3) ran with the MAF disconnected
4) replaced as many vacuum lines as I could get to (at the front of the engine most were quite bad)
5) given the engine some full throttle / high rpm runs

I "think" the vacuum line replacements made a slight improvement to the rough idle / misfire the engine has always had but made no change to the hesitation

My next steps are to start replacing parts like fuel filter etc, I was told to change the K40 relay but mine is a 2003 model which I believe does not have the K40 relay (?)

The car stood for about 3 months whilst I had some rust repairs done, replaced brakes etc but ran fine after that. I left the interior light on and flattened the battery and I think this is when the problem started. Could it be related to a flat battery ? After charging the battery up it has held a charge fine and starts up easily.

Has the throttle position sensor lost its setting after a flat battery situation ?

Could the fuel pump be dying ? If so I would have thought under load it would be playing up too ?

I have a basic OBD checker but the only code showing related to the charcoal evap system and I have always had that error for 12+ years, even Mercedes said to ignore it

The hesitation can be quite severe, almost like the engine is going to stall completely but then it just picks up and clears. In all other driving situations everything seems ok

Help !

Edited by darko 4/14/2019 1:45 PM
#240603
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Author
Posted 4/14/2019 6:58 PM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
RE: Hesitation after slowing or stopping at junctions

Your problem is a simple one and has a simple answer. Your vehicle has two-too-many wheels for driving on the island. Sorry, my endless lust to see the TT in person one day meant I couldn't resist.

But in the "trying to actually help" mode, I think it would be good to verify the voltage present in the primary wiring. The battery might not be as good as you think. I've had batteries that started the car 100% reliably but had ZERO reserve. I never knew it until it was too late. When I had similar conditions in my 460 back when it was a 2.8L petrol the issue was the ignition coil itself. My mechanic diagnosed and fixed it as I was completely baffled thinking a coil would play up under HIGH demand, not low. But in my case the coil wasn't functioning well when the car's voltage was a little lower at idle than it was when revs were higher.

So anyway, just some thoughts.

Good luck!

-Dave G.
#240605 - in reply to #240603
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Posted 4/15/2019 4:14 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

Aha ! True, however I am abiding by Manx rules and have a motorbike in the garage too

I did a bunch of googling last night and found someone had a similar issue on a SL55 AMG - it turned out to be the EVAP / Charcoal canister so perhaps I should stop ignoring that issue now

The thread is here :

https://mbworld.org/forums/sl-class-r230/694073-help-sl55-amg-interm...

It turned out some kind of valve had gone bad near the charcoal canister and was allowing fuel to go into the EVAP system (not just fuel fumes) and replacing this valve cured the problem

Whilst we had the rear bumper off for painting and doing some wax oiling treatment I noticed a smell of fuel in the rear wheel arch, near the the fuel cap and charcoal canister. If it is flooded this could be the problem. I will check today once the whether improves.

I also notice someone having a similar issue in a post further down on their G500 :

http://www.pointedthree.com/disc/forums/showthread.asp?tid=24037&mi...
#240606 - in reply to #240603
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Posted 4/15/2019 4:15 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

By the way Dave G you MUST come to the TT !!
#240607 - in reply to #240603
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Posted 5/5/2019 4:10 PM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
RE: Hesitation after slowing or stopping at junctions

darko - 4/15/2019 2:14 AM

Aha ! True, however I am abiding by Manx rules and have a motorbike in the garage too

I did a bunch of googling last night and found someone had a similar issue on a SL55 AMG - it turned out to be the EVAP / Charcoal canister so perhaps I should stop ignoring that issue now...


Well? Did you fix it? Good job digging out that potential cause. I hope it's an easy fix.
-Dave G.
#240657 - in reply to #240606
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Posted 9/15/2019 1:50 PM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
Re: Hesitation after slowing or stopping at junctions

Hi, sorry for the lack of reply, its been a busy summer

so... I haven't got to the bottom of this fault sadly. I have an LPG conversion on the car and it runs fine on LPG so I suspect its a problem in the fuel system (fuel pump / fuel filter / fuel evap canister)

Should have some more time to look into it soon
#240992 - in reply to #240657
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Posted 9/22/2019 11:54 AM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
Re: Hesitation after slowing or stopping at junctions

darko - 9/15/2019 11:50 AM
...I haven't got to the bottom of this fault sadly. I have an LPG conversion on the car and it runs fine on LPG so I suspect its a problem in the fuel system (fuel pump / fuel filter / fuel evap canister)...


Bummer. Are you able to check the injector signals at the injectors? Do some searching of this forum and others on injector wiring harness issues. I think vehicles in that timeframe might have had a problem with that portion of the harness, but could be mis-remembering. Your mention of running well on LPG is telling because that's probably a "fogging" sort of system near the throttle body, not relying at all on the petrol injectors, correct?

Best of luck!

-Dave G.
#241003 - in reply to #240992
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Posted 11/23/2019 7:21 PM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

So, an update to this problem...

The LPG system started having issues too so I decided to get into working this fault out

Firstly I followed G-AMG's guide on replacing the fuel filter here : http://www.pointedthree.com/disc/forums/showthread.asp?tid=12695&po...

jumped in and drove round the block - problem still there (sadly) but at least the car has a fresh fuel filter!

Next I decided to remove the throttle position sensor and check / clean it up, as its a sealed unit not much I could do but, after re-fitting I followed the procedure for resetting the throttle sensing / travel :

01 - Turn the key to ON position. Position II that is. Don’t start the car.
02 - Press and hold the gas pedal for at least five seconds. Keep the pedal pressed.
03 - Turn ignition off but do not remove the key. Now release the gas pedal.
04 - Remove key. Wait a minute before you restart your Mercedes.

Drove round the block and amazingly the problem seems to have gone !

I "think" I can still feel a small hesitation but nothing like how bad it was, I have ordered a new throttle position sensor (part no. A0125423317) and will replace the old one to be 100% sure

LPG system seems happy too so maybe that was getting freaked out by unexpected signals form the throttle sensor ?

Will update further once the new sensor arrives...
#241234 - in reply to #240603
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Posted 12/22/2019 11:29 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

So a follow up on this...

New throttle position sensor was fitted and a few miles later the same problem returned - this one is driving me crazy....!!

Today I went through as much as I could on the engine bay, checking and double checking

I also drove with the MAF connected and then disconnected - no difference - hesitation is still there

I found a large vacuum leak from the bottom of the manifold (in red) a bit of research showed this to be a well known issue, out of interest I removed the air pump (emissions) and re-routed some of the vacuum hoses (in blue). Driving the car seems to be smoother and have a bit more 'go'. I have always found the performance inconsistent and wonder if this was due to the vacuum leak not operating the variable intake properly? Idle also seems better, this has always been a bit rough especially when hot


Either way, this has not made any difference to the hesitation (annoyingly!) but good to fix anyway


I drove around a few roundabouts to try and narrow down this problem:

Hesitation appears to happen at slower speeds only, sub 15mph.

Left hand corners seem worse than right

There is a momentary loss of power / hesitation

Occasionally happens after slowing down and stopping. When pulling away the car sounds like its getting either flooded or running out of gas

I have a new OBDII dongle arriving next week, the USB one I use for my bikes does not seem to work, Hopefully there will be some codes to try and point me in the right direction...

In the mean time if anyone has any ideas, I am all ears !





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#241332 - in reply to #240603
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Posted 12/22/2019 1:47 PM
gbenzer
Extreme Veteran




Date registered: Dec 2006
Location: Georgia
Vehicle(s): 2007 G-500, 2017 Audi Q7
Posts: 418
300
RE: Hesitation after slowing or stopping at junctions

I hesitate to jump in with all the expert ideas expressed, no pun intended, but could something be putting the engine into limp mode? I know that my ABS problem puts mine into limp mode and it is no fun to drive because of decreased output power especially at <20mph. I know your frustration because my ABS light issue has been with me for many years and no one can figure out what the problem is. Good luck.
#241333 - in reply to #241332
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Posted 12/22/2019 2:09 PM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
Re: Hesitation after slowing or stopping at junctions

Interesting idea...

If going into limp mode will the car come out of limp without a re-start?

If it is in limp mode it only happens briefly (less than 3 seconds) and then drives normally (engine not re-started)

When the engine hesitates it almost feels like traction control intervention or as mentioned before fuel starvation or over fuelling

Ive just had a thought - I might try driving with the traction control (ASR) switched off and see what happens - maybe it getting a bad signal and triggering it somehow (I haven't seen the warning light come on though)

I guess its something else to try though!
#241334 - in reply to #241333
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Posted 12/22/2019 2:23 PM
gbenzer
Extreme Veteran




Date registered: Dec 2006
Location: Georgia
Vehicle(s): 2007 G-500, 2017 Audi Q7
Posts: 418
300
Re: Hesitation after slowing or stopping at junctions

darko - 12/22/2019 2:09 PM

Interesting idea...

If going into limp mode will the car come out of limp without a re-start?

If it is in limp mode it only happens briefly (less than 3 seconds) and then drives normally (engine not re-started)

When the engine hesitates it almost feels like traction control intervention or as mentioned before fuel starvation or over fuelling

Ive just had a thought - I might try driving with the traction control (ASR) switched off and see what happens - maybe it getting a bad signal and triggering it somehow (I haven't seen the warning light come on though)

I guess its something else to try though!

Mine stays in limp mode until restarted. Since it's the ABS/ESP system causing the problem I also don't have cruise control and it won't reset until I restart the G. My problem is apparently something in the front left "vehicle speed sensor" circuits. I don't know if turning ASR off puts it into limp mode but I don't think it should.
#241335 - in reply to #241334
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Posted 12/23/2019 10:10 AM
King_GH
Extreme Veteran




Date registered: Oct 2011
Location: London
Vehicle(s): 95 G300 RHD
Posts: 323
300
Re: Hesitation after slowing or stopping at junctions

Hi there
I ran into a similar problem last year on my trip to France. There's never an issue when starting the car and it drives perfectly until you get to a junction or slow down to a halt. Suddenly it hesitates and sometimes switches off. I cleaned everything there was to clean and then started thinking about things I could start changing until I started checking the forums and read about a guy who had a similar problem and listed all the parts he had to change. I didn't mind changing them but I was in France... where do I go to find parts in some remote part of town? However it appeared that what resolved it was a change in fuel type. I used a gas station who had contaminated their fuel with some of the unholy corn fuel aka ethanol.
My advice is this; before you spend too much time, simply switch your fuel station for a brief period or maybe even where you get your LPG and see what effects it has. That evening I drove about 60 miles to find me a Shell and filled the tank with good old Vpower and that was then end of that problem.

Edited by King_GH 12/23/2019 10:13 AM
#241338 - in reply to #241334
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Posted 12/23/2019 10:52 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

Fuel quality has definitely been something i have been thinking about, problem is, here in the Isle of Man most petrol stations are the same and get the fuel from the same source..

I would definitely stick some Shell V power in if I could get it but I can't - I have put some fuel additive in today to see if the helps

I have driven around for about 2 hours today and the hesitation is still there, always at slow speed either after turning corners or pulling out at junctions (quite scary sometimes!!)

Having had other strange gremlins with the car a few years back I remembered that a new battery and voltage regulator fixed those completely (weird warnings on dash board etc)

So, today I bought a new battery, the last one was bought new from Mercedes in september 2015 so is almost 4.5 years old

Even after driving around for 2 hours the battery in the car only measures 12.25V. By comparison the new battery straight of the shelf in the shop measures 12.83V

From what I have read, 12.25V shows the battery is only at 50% capacity so perhaps at slow engine speed (with no alternator voltage input) the battery cannot supply the systems of the car with enough voltage (Fuel pump / ECU / Solenoids etc etc)

I have put the new battery on an Optimate conditioner overnight just to be sure its in perfect shape before I fit it tomorrow

Really hoping the new battery might be the fix but again it definitely needed doing anyway..




Edited by darko 12/23/2019 10:55 AM




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#241340 - in reply to #240603
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Posted 12/23/2019 11:24 AM
King_GH
Extreme Veteran




Date registered: Oct 2011
Location: London
Vehicle(s): 95 G300 RHD
Posts: 323
300
RE: Hesitation after slowing or stopping at junctions

So there's a possibility that some bright spark has started to gently introduce E10 fuel to Isle of Man. Still that will be hard to prove and how do you even test the fuel?
#241341 - in reply to #241340
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Posted 12/23/2019 2:16 PM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
5000
RE: Hesitation after slowing or stopping at junctions

King_GH - 12/23/2019 11:24 AM

So there's a possibility that some bright spark has started to gently introduce E10 fuel to Isle of Man. Still that will be hard to prove and how do you even test the fuel?


In the USA, the fuel pump must be marked advising if the fuel contains the damned ethanol.
#241344 - in reply to #241341
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Posted 12/24/2019 11:14 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

DUTCH - 12/23/2019 8:16 PM

King_GH - 12/23/2019 11:24 AM

So there's a possibility that some bright spark has started to gently introduce E10 fuel to Isle of Man. Still that will be hard to prove and how do you even test the fuel?


In the USA, the fuel pump must be marked advising if the fuel contains the damned ethanol.



Wish that was the case here, the fuel tank on my motorbike swelled by about 5% in size thanks to Ethanol in the UK...
#241348 - in reply to #241344
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Posted 12/24/2019 11:20 AM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

Well my new OBD-II dongle arrived today so I managed to pull some codes, the first 2 (P0446 & P0451) have been on the car since I bought it, when I spoke to Mercedes abut fixing them they suggested I shouldn't worry (so I haven't)

The other 2 codes (P0102 & P0112) are new - Looks like they are pointing to the MAF unless the W463 uses a separate Air Temperature Sensor ?

Bank 1 Sensor 1 - this suggests there might be another Intake Air Temperature Sensor but I'm not sure

I tried clearing the codes but they come straight back






(01-DTC P0446.jpg)



(02-DTC P0451.jpg)



(03-DTC P0102.jpg)



(04-DTC P0112.jpg)



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#241349 - in reply to #240603
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Posted 12/24/2019 1:41 PM
darko
Regular


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 62
50
RE: Hesitation after slowing or stopping at junctions

Also looks like I might still have a vacuum leak on bank 2 of the engine - there is a "long term fuel trim bank 2" of 0.8% - not a huge leak I guess





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#241350 - in reply to #240603
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Posted 12/24/2019 4:32 PM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 828
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RE: Hesitation after slowing or stopping at junctions

King_GH - 12/23/2019 11:24 AM

So there's a possibility that some bright spark has started to gently introduce E10 fuel to Isle of Man. Still that will be hard to prove and how do you even test the fuel?


https://www.autofuelstc.com/fuel_testing.phtml in the right hand column is the instructions.

or

https://www.pure-gas.org/about about half way down

Is it possible that the station(s) are selling lower octane fuel despite the "label" on the pump? Will your test kit be able to tell you if the knock sensor is picking up a signal or if the timing is retarding?

Edited by J.R. 12/24/2019 4:43 PM
#241351 - in reply to #241341
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